Cathode ray oscillator



Jan. 11, 1938. c R N 2,104,834

CATHODE RAY OSCILLATOR Filed Dec. 15, 1933 -:.ll L

INVENTOR, BERNARD C. GARDAER.

ATTORNEY v Patented Jan. 11, 1938 UNITED STATES PATENT OFFICE CATHODERAY OSCILLATOR poration of California Application December 13, 1933,Serial No. 702,141

4 Claims.

My invention relates to a cathode ray oscillater, and more particularlyto such an oscillator wherein the beam is collimated with respect to thetargets,

Among the objects of my invention are: to provide a cathode ray tubehaving a collimated beam; to provide a cathode ray tube oscillator inwhich the beam is collimated with respect to the targets; to provide ameans and method for 101 collimating a cathode ray beam; to provide ameans and method of regulating the cross section of a cathode ray beam;to provide a means and method of causing a cathode ray beam to divergein certain directions only; to provide a means and method ofpredetermining the cross sectional shape of a cathode ray beam, toprovide a cathode ray oscillator requiring a. minimum of beamdeflection; to provide a means and method of regulating the waveform ofthe 9 output of a cathode ray oscillator; and to provide a highlyeflicient cathode ray oscillator tube.

Other objects of my invention will be apparent or will be specificallypointed out in the descripu tionforming a part of this specification,but I do not limit myself to the embodiment of the invention hereindescribed, as various forms may be adopted within the scope of theclaims.

Referring to the drawing: 1

g In the drawing which illustrates a preferred form of cathode rayoscillator tube, illustrating the method and a preferred embodiment ofmy invention, Figure 1 is a longitudinal sectional view, the centralportion having been broken away ll for ease in illustration.

Figure 2 is a cross sectional view taken as indicated by the line 2-2 inFigure 1, but rotated 90 clockwise about the longitudinal axis of thetube for ease of illustration.

40 Figure 3 is a longitudinal sectional view oLthe target structuretaken as indicated by the line 3-3 in Figure 2. This figure has alsobeen rotated 90 clockwise about the longitudinal axis of the tube, asshown in Figure 1.

Figure 4 is a cross sectional view of the electron gun only, taken asindicated by the line 4-4 in Figure 1.

Although there are many types of structure known in the art whichutilize a cathode ray beam which is moved across a shutter to produce analternating current, most of these oscillators pay no attention to theshape or relative cross sectional dimensions of the beam. As some of theoutput energy must be used to move the beam I in order that the tube becapable of sustained a1- ternations, it is obvious that the smaller theamount of energy which is needed to move the beam from one of thetargets to the next, the more eflieient the device will be. Heretoforetarget spots have been made exceptionally small in 5 order that themovement may be made short, but this has resulted in high electrondensities at the point of impact, causing loss by the production of heatin the target. I have found that it is possible to extend the beam overa wide area in 0 one dimension, retaining the other dimension at aminimum. I thus cause the beam to cover a large area on the target, andby causing the rectangular cross section of the beam to be collimatedwith respect to the division between targets, I am able to get acomplete transfer of energy from one target to another with a minimumdeflection.

In broad terms, as'to the oscillator itself, my invention comprises apair of targets, and means for generating a cathode ray beam collimatedwith respect to the division between the targets. My preferred method ofcollimating the beam, in broad terms, is to apply an accelerating fieldto a. beam of electrons, in which field some of the lines of force areparallel while others are divergent to cause the beam to spread alongcertain dimensions but not in others. The method,

therefore, may be used not only for collimation but also to obtain beamsof various odd sym- 3O metrical or nonsymmetrical cross sectionalshapes. By oscillating beams of various shapes across the division linebetween targets, it will be obvious that an output waveform ofpractically any contour desired may be obtained. The apparatus used toshape the beam comprises, in broad terms, an emitter and a perforatedanode positioned to accelerate the electrons through the perforation,when energized, the anode being so shaped as to apply a field in whichthe angles of the lines of force vary circumferentially around thebeam.

As an illustration of my invention, I have chosen a cathode rayoscillator'wherein the beam is shaped to give a rectilinear spot on apair of targets, this spot being collimated with respect to a divisionbetween the targets. Modification of the apparatus to produce spotsother than the rectilinear example here shown will be obvious to thoseskilled in the art. Referring to the drawing, an envelope I, preferablyof the usual .tapered shape having a wide end 2 and a stem end 4 isprovided with, at the stem end, a reentrant stem 5, the inner end ofwhich is closed by a pinch 6. A central grid lead I is sealed throughthe middle of the pinch and supports a.,

control electrode 9 which is in the form of a trough opening toward thefar end of the tube. on each side of the control lead l are cathodeleads l0 supporting a filamentary cathode H which passes longitudinallythrough the trough. It is desirable that this cathode be relativelyheavy, a good emitter, and not be materially longer than the length ofthe emitting portion desired. In order, therefore, that the cathode neednot be lengthened to extend outside the trough, I prefer to provide thecathode leads ID with bends I! so that the joint between these leads andthe filament may lie inside the trough if desired.

Certainfilamentarymaterials do not have a large linear expansion whenheated. Others do. When one of the latter materials is used I prefer tobreak one of the cathode leads and insert in the break a spring l4 bentto take up the slack in the filament when heated, and thus prevent thefilament buckling out of its proper position. It is also desirable thatthe cathode leads be of relatively heavy material having good heatconductivity so that the ends of the filament will not heat to emissivetemperature adjacent the junction. In other words, I prefer to confinethe heating and consequent emission to the central portion only of thefilament, and the length of this emissive portion may be determined bythe relative sizes of the filament and the leads to which it isattached.

Immediately adjacent the emitter I position an accelerating anode l5supported by anode risers l6 welded to a stem clamp II. An anode lead l9passing through the stem seal provides outside electrical connection tothe anode. The anode is preferably formed from a plate having arectilinear aperture 20 therein, the edges of this aperture beingprovided with longitudinal lips bent and extending toward the filamentto form a slit 2| parallel to the filament and in line with the oppositeend of the tube. It is desirable that these lips converge slightly sothat the slit is somewhat smaller in width than the aperture. Both theslit and the aperture are preferably materially longer than the emissiveportion of the filament, the anode being so positioned that the emissiveportion of the filament is centrally 10- cated with respect to theaperture and slit.

The wide end of the tube 2 is provided with a pair of targets 22supported by target leads 24. Each of these targets is substantially ofsemicircular shape, positioned so that their straight sides areadjacent, one of the targets preferably being provided with a bend 25overlapping the straight side of the other target. The division linebetween the two targets is thus a straight line, and preferably shouldextend at right angles to the line of the filament and the anodeaperture. It is also desirable that the plates have an angularrelationship. In the tube illustrated, the plates are positioned to forma right angle, the point of the angle being directed away from thecathode.

In operation the tube is more scanning coils provided with one or 26,positioned so that their magnetic field, when energized, will deflectthe beam from one target to the other. When current is passed throughthe cathode a short portion in the center'of the filament bocomes heatedand emits electrons. Voltage applied on the anode draws the emittedelectrons through the slot 2|, to form the beam. Proper tuned circuitsmay be connected to the targets and a certain amount of the outputenergy fed through the scanning coils 26 in such a manner that the beamis continually oscillated across the target division line. Analternating current is thereby produced.

The cross sectional shape of the beam is largely determined by the shapeof the anode. In the figures, the path of the beam is shown by the longdash line 21, and the outline of the impact area of the beam by theshort dash line 28. It will be noticed that the beam is extended along aline at right angles to the line of the filament and anode slot.Referring to the Figures 1 and 4 which give two sectional views of thegun, it will be noticed, in Figure 4, that electrons leaving thefilament are caused to diverge due to the field divergence to the anodelips, and after leaving the anode aperture the beam expands rapidly inthe planes at right angles, or normal to the slot. However, as only thecentral portion of the filament is emissive and the slot and apertureare materially longer tha the emissive portion of the filament, there isno tendency to spread the beam longitudinally of the slot. In otherwords, the lines of force from the edge of the lips nearest to thefilament are substantially parallel in the planes parallel with thefilament, but are converging in a plane normal to the filament, thusfanning out the beam to have a long dimension at right angles to thefilament. As the lips of the anode which form the yond the emissiveportion of the filament, the lines of force are parallel in the planethrough the lips and the filament to a point well beyond the emissiveportion. It will be noted that the ends of the anode channel are bar 29in the illustration shown. This bar does not change the fieldconditions, however, but simply maintains the lips in proper spacedrelationship.

It will be obvious that many cross sectional patterns may be produced byfollowing out the methods above disclosed. By changing the angles of thelines of force the beam can be made to diverge more or less in certaindirections and not at all in others. The cyclical passage of variouslyshaped beams across the division line between the targets will obviouslyproduce an output having waveforms related to the shape of the beam. Inthis manner I have been able to obtain, for example, sawtooth waveshaving definite angles. Other applications of the methods and apparatusfor various purposes will be apparent to those skilled in the art.

I claim:

1. In an oscillator wherein an alternating current is produced by acathode ray beam of elongated initial cross-section cyclicallycontacting an adjacent pair of electrodes overlapping to form a singlelinear division line therebetween, said division line being normal tothe long dimension of the initial beam cross-section, the method ofoperation which comprises spreading said beam to form a spot on saidelectrodes elongated in a dimension parallel to the division linebetween said electrodes and normal to the long dimension of the initialbeam cross-section, and cyclically moving said beam from one side ofsaid division line to the other.

2. In an oscillator wherein an alternating current is produced by acathode ray beam cyclically contacting an adjacent pair of electrodeshaving a single linear division line therebetween, said beam having anelongated cross-section initially normal to said division line, themethod of opclosed by an angle slot project beeration which comprisesspreading said beam to 75 form a spot on said electrodes elongated in adimension parallel to the division line between said electrodes, andcyclically moving said beam from one side of said division line to theother.

3. In an oscillator wherein a cathode ray beam cyclically contactsadjacent electrodes having a single, linear, division line therebetween,the method of producing an alternating current which comprises producingsaid beam with a cross-section elongated normally to the said divisionline, maintaining the initial length of said beam section normal to saiddivision line, spreading said beam parallel to said division line,deflecting said spread beam normally across said division line, andcollecting said beam alternately upon said electrodes adjacent the lineof division.

4. In a cathode ray tube oscillator, the method of operation whichcomprises generating electrons from a line source, restraining theelec-= trons from diverging in planes parallel to the said source,causing said beam to diverge in planes perpendicular to said source,deflecting said beam cyclically about an axial position after divergenceand normal to the direction of such divergence, and collecting said beamduring deflection from said axial position.

BERNARD C. GARDNER.

